1. Field of the Invention
The present invention generally relates to a data conversion system and method, and more particularly, to a system and method for converting analog data to digital data using visual images.
2. Description of the Related Art
In the processing industry it is generally important to be able to monitor on-going processes. Specifically, in the semiconductor processing industry, it is important to monitor, such parameters as temperature, pressure, and mass flow rate.
In a typical semiconductor processing system, a mass flow controller, for example, is a well-known instrument used to maintain a preselected mass flow rate. A typical mass flow controller operates on the principle of adding heat energy to a flowing fluid and measuring a heat transfer function and or thermal mass transport function in two sensors spaced in or near the flowing fluid. The measure of the temperature difference between the sensors is a function of fluid mass flow. When the fluid at one temperature having passed by the first upstream sensor is then heated to a higher temperature, the resistivity of the downstream second sensor is changed, the measured temperature difference between the sensors being the measure of flow. In a gas, the rise in temperature is a function of the amount of heat added, the sensor geometry and conductivity, the mass flow rate and the properties of the gas.
In FIG. 1, an example of a typical mass flow controller 10 is shown, which includes a horizontal bypass sensor tube 12 with upstream and downstream sensors 14 and 16, respectively, exterior of the tube and a heater element 18 similarly wound between sensors 14 and 16 on the tube exterior. When fluid (liquid or gas) is flowing in tube 12, heat is transferred along the line of flow from upstream sensor 14 to downstream sensor 16 producing a signal. Each sensor 14 and 16 form part of a bridge and amplifier circuit, which can detect the temperature difference caused by the greater heat input to the downstream sensor 16, and can produce a signal proportional to the gas flow rate. The flow rate signal is compared to a command voltage from a potentiometer or the like, which generates an error signal. The error signal causes a valve to change the flow rate until a predetermined flow rate has been reached.
Unfortunately, the mass flow controller, thus described, has several drawbacks. For example, heat conduction is through the tube wall, which may result in relatively long response times. To provide satisfactory performance, this type of mass flow controller generally requires heating of the fluid up to about 100xc2x0 -200xc2x0 C. greater than the ambient temperature of the incoming fluid. In many gaseous applications, this may be above the safe temperature limit of the gas or cause decomposition of the gas or reaction with contaminants. Moreover, the heater element requires greater amounts of power. Further, for each gas composition and flow range, the instrument must be calibrated because of nonlinearities and inconsistent correction factors.
For this reason, what is needed is an improved system and method for obtaining data related to the operation of a processing system, which is less complex to implement, less expensive to put into practice, and more reliable than currently existing systems and methods. The system and method should include the ability to convert analog data obtained from various meters and gages, to a digital data signal useable for operating various control devices.
The present invention provides an improved system and method for obtaining data related to the operation of a processing system, such as a semiconductor processing system. Advantageously, the present invention provides conversion from analog measurement data, usually obtained from meters and gages, to digital data, which is typically more useful for operating various control devices.
The present invention provides a system for collecting visual images of various types of measuring instruments, which are used for measuring a process functionality, such as mass flow rate, temperature, pressure, and the like. An image sensor is included in the system for providing an image of a first feature of the measuring instrument. The image data is processed by an image processor, which is operable to detect the first feature and determine its position relative to a second feature of the measuring instrument, which is the measured value. The measured value can then be compared to a predetermined or expected value. If the measured and expected values are not substantially the same (within an acceptable limit), a signal can be generated which instructs a controller to adjust the process functionality until the measured value reaches the expected value.
The present invention compares digitally formatted data rather than, for example, temperature differences (see FIG. 1) and is therefore less complex to implement, less costly to put into practice, and more reliable then typical mass flow controllers. Advantageously, the present invention may provide uninterrupted measurement using readily available and easily implemented conventional measuring instruments. The application of the present invention is flexible in that the invention can be used to monitor measuring instruments that currently exist on processing systems without having to change out the instruments.